1. Field of the Invention
The present invention relates generally to cabling and wiring arrangements and, more particularly, to cabling for transmitting signals between components of an implantable medical device.
2. Related Art
The use of medical devices to provide therapy to individuals for various medical conditions has become more widespread as the advantages and benefits such devices provide become more widely appreciated and accepted throughout the population. In particular, devices such as hearing aids, implantable pacemakers, defibrillators, functional electrical stimulation devices such as cochlear prostheses, organ assist or replacement devices, and other medical devices, have been successful in performing life saving and/or lifestyle enhancement functions for a number of individuals.
Many such medical devices often include one or more sensors, processors, controllers or functional electrical components that are permanently or temporarily implanted in a patient. Many such implantable devices require the transfer of power and/or information with external components that are part of, or operate in conjunction with, the implanted components of the medical device. One common approach to provide for the transcutaneous transfer of power and information with an implantable component is via a transcutaneous transfer system which couples patient-worn components with the implanted components.
One such type of medical device is a cochlear implant system. Cochlear implant systems provide the benefit of hearing to individuals suffering from severe to profound hearing loss. Hearing loss in such individuals is due to the absence or destruction of the hair cells in the cochlea which transduce acoustic signals into nerve impulses. Cochlear implants essentially simulate the cochlear hair cells by directly delivering electrical stimulation to the auditory nerve fibers. This causes the brain to perceive a hearing sensation resembling the natural hearing sensation normally delivered to the auditory nerve.
Conventional cochlear implant systems primarily include an external assembly directly or indirectly attached to the body of the patient (sometimes referred to herein as the recipient), and an internal assembly which is implanted in the patient. The external assembly typically comprises one or more microphones for detecting sound, a speech processing unit that converts detected sound into an electrical coded signal, a power source, and an external transcutaneous transfer coil. The internal assembly typically comprises an internal transcutaneous transfer coil, a stimulator unit located within a recess of the temporal bone of the recipient, and an electrode array positioned in the recipient's cochlear.
Collectively, the external transcutaneous transfer coil and the internal transcutaneous transfer coil form an inductively-coupled coil system of a transcutaneous transfer system. The transfer of energy via this system is controlled to effect the transmission of the electrical coded signals, referred to herein as stimulation signals, and power signals from the external speech processing unit to the implanted stimulator unit. Similarly, the transcutaneous transfer system may be used to effect the transmission of telemetry data from the implanted stimulator unit to the exterior speech processing unit. Conventionally, the communications link has been in the form of a radio frequency (RF) link, although other such links have been proposed and implemented. Once a stimulation signal has been transmitted to the implanted transcutaneous transfer coil, it is provided to the implanted stimulator unit which processes the signal and outputs one or more signals to the intra-cochlear electrode assembly which applies the electrical stimulation directly to the auditory nerve of the recipient.
There are two common arrangements of the noted external assembly components. In one arrangement, the microphone(s) is/are combined with the speech processing unit in a so-called “behind-the-ear” configuration. In such a configuration, the external coil is a separate unit connected to the speech processing unit via a cable. In the other common arrangement, at least one microphone is combined with the external transmission coil. If one or more additional microphones are included in the speech processing unit, then the speech processing unit is designed to be worn behind the ear and is connected to the external coil via a cable. On the other hand, if the speech processing unit does not include a microphone it may be designed to be worn on the body of the recipient and connected to a headset unit worn behind the ear via a cable. The headset, in turn is connected to the external coil via a second cable.